Compositions comprising solid solutions of chlorinated paraffin and gamma benzene hexachloride



United States Patent COR POSITIONS COMPRISING SOLID SOLUTH'ONS 0F CHLORINATED PARAFFIN AND GAMMA BENZENE IEXACHLORIDE Hyatt Henry Spendlove, Bovingdon, Maidenhead, and

Alastair Campbell, Widnes, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain 7 v g No Drawing. Filed Nov. 19, 1958, Ser. No. 774,837

Claims priority, application Great Britain Dec. 2, 1957 9 Claims. (Cl. 167-42) .The present invention relates to improvements in or relating to compositions comprising benzene hexachloride and more particularly to Water dispersible pesticidal pulverulent compositions comprising gamma benzene hexachloride.

A known disadvantage of gamma benzene hexachloride is that the pesticidal activity of its deposits may not be sufiiciently persistent and to overcome defect compositions comprising for instance gamma benzene hexachloride and one or more fusible materials solid at room temperature and having a lower vapour pressure than the I hexachlorocyclohexane have been proposed and in order to show that these compositions give deposits which are more persistent in their pesticidal activity than compositions of the same percentage strength of gamma benzene hexachloride which do not contain any of the aforesaid fusible material, Petri dishes have been employed as deposition surfaces.

It has been experimentally ascertained however that although, for example, by spraying solutions containing 2 parts of coumarone resin to one part of gamma benzene hexachloride, more persistent deposits are obtained on non-absorbent surfaces than solutions containing gamma benzene hexachlcride alone there is no increase in persistence on absorbent surfaces. It is however on such surfaces as that of lateritic mud, which is the material used in some tropical regions for building mud huts, that much antimalarial spraying is carried out.

The object of the present invention is to provide water dispersible pesticidal pulverulent compositions comprising gamma benzene hexachloride which when deposited as by spraying of their water dispersions on sorptive and non sorptive surfaces give deposits which have a more persist ent pesticidal activity than heretofore.

It has now been found that deposits of improved pesticidal persistency can be formed on sorptive and non sorptive surfaces from water dispersible pesticidal pulverulent compositions comprising an admixture containing gamma benzene hexachloride and at least one resin in intimate association wherein the ratio of gamma benzene hexachloride to resin is such that for vapour pressures measured by effusion at 50 C. the vapor pressure of the gamma benzene hexachloride is less than 75% of the vapour pressure of free gamma benzene hexachloride and after 25% has evaporated at 50 C. the vapour pressure is less than 25% of the vapour pressure of free gamma benzene hexachloride. For example, it has been found that the water dispersible pulverulent compositions can have a composition wherein in said admixture the ratio of gamma benzene hexachloride to resin is such that the vapour pressure of the gamma benzene hexachloride is less than 20% of the vapour pressure of free gamma benzene hexachloride and after 6% has evaporated at 50 C. the vapour pressure is less than 8% of the vapour pressure of free gamma benzene hexachloride.

According to the present invention a water dispersible pesticidal pulverulent composition comprises an admixture containing gamma benzene hexachloride and at least one resin in intimate association wherein the ratio of gamma benzene hexachloride to resin is such that for "icevapour pressures measured by effusion at 50 C. the vapour pressure of the gamma benzene hexachloride is less than of the vapour pressure of free gamma benzene hexachloride and after 25 has evaporated at 50 C. the vapour pressure is less than 25% of the vapour pressure of free gamma benzene hexachloride.

By way of example said water dispersible pesticidal pulverulent composition can be one wherein in said admixture the ratio of gamma benzene hexachloride to resin is such that for vapour pressures measured by effusion at 50 C. the vapour pressure of the gamma benzene hexachloride is less than 20% of the vapour pressure of free gamma benzene hexachloride and after 6% has evaporated at 5 0 C. the vapour pressure is less than 8% of the vapour pressure of free gamma benzene hexachloride.

Because the aforesaid admixtures in the aforesaid water dispersible pesticidal compositions have a vapour pressure less than 25% of free gamma benzene hexachloride only after 25% has evaporated at 5 0 C., or, for example a vapour pressure less than 8% of free gamma benzene hexachloride only after 6% has evaporated, it is assumed, because rate of evaporation is a function of vapour pressure, that the rate of evaporation of the gamma benzene hexachloride in said water dispersible pesticidal composition will be less than the rate of evaporation of free gamma benzene hexachloride.

Said water dispersible pesticidal pulverulent compositions may be pulverulent compositionsof a powdered solidified melt of an admixture comprising gamma benzene hex-achloride and at least one resin in the aforesaid ratios.

The preferred resins are solid chlorinated paraffins, for example the solid chlorinated paraffin waxes and in particular the solid chlorinated paraffin wax Cereclor 70. Cereclor is a registered trademark. Cereclor 70 is a solid chlorinated paraflin wax having an average chlorine content of 70%, a freezing point of between 70 and C. and a specific gravity of 1.63.

Satisfactory results have been obtained on sorptive and non sorptive surfaces from pesticidal pulverulent compositions which contained garnrna benzene hexachloride to a solid chlorinated paraflin wax containing 65-75% chlorine, for example Cereclor 70, in a 3:1 ratio but the best results have been obtained from pesticidal pulverulent compositions wherein the ratio of gamma benzene hexachloride to a solid chlorinated parafiin wax containing 65-75% chlorine, for example Cereclor 70, has been not higher than 21-1 and often when said ratio is not much higher than 1:1. In other words, although satisfactory results have been obtained on sorptive as well as non sorptive surfaces when the gamma benzene hexachloride did not exceed 75% by weight on the combined weight of the gamma benzene hexachloride and the solid chlorinated parafiin, particularly a solid chlorinated paraflin wax containing 65-75% chlorine, for example Cereclor 70, it is often preferred for the gamma benzene hexachloride not to exceed 55% by weight on the combined weight of the gamma benzene hexachloride and the solid chlorinated parafiin, particularly a solid chlorinated paraflin wax containing 65-75% chlorine, for example Cereclor 70.

Examples of water dispersible pesticidal pulverulent compositions according to the invention are those comprising a solid chlorinated par-aflin, as for instance -a solid chlorinated parafiin wax, particularly Cereclort.70, and gamma benzene hexachloride where-in the gamma benzene hexachloride does not exceed 75 by weight, and, for instance, does not exceed 50% by weight on the combined weights of the solid chlorinated paraflin, or for instance, the solid chlorinated paraflin Wax, and the gamma 3 V benzene hexachloride. These water dispersible pesticidal pulverulent compositions may contain diluents as for example "a china clay and various dispersing and wetting Percent Gamma benzene hexachloride/Cereclor 70 (3:1) or gamma benzene hexachloride/Cereolor 70 (2:1) or gamma benzene hexachloride/Camelot 70 (1:1) 50 Fullers earth 4O A sodium alkyl aryl sulphonate 8 A sodiumalkylnaphthalene sulphonate 2 V The 3:1 and i221 gamma benzene hexachloride/Cere- Table 2 Vapour Pressure Relation to Percent Initial Evaporated Sample vapour pressure,

mm. mm. Hg Percent at 50 C. evaporated at 50 C.

"Aroclor 5460 (a chlorinated polyphenol) 7. 9X10 3. 5X10 V 34 A para tertiary oetyl phenol resin. 6. 4X10- 2. 7X10- 35 A coumaroue resin, M.P. v 75-85O 6. 2X10 3. 4X10 41 A phenolic terpene resin 5. 6X10- 2. 8X10- 29 A modified phenolic terpene resin. 5. 4X10' 2. 0X10 '35 clor 7 O pulverulent compositions were found to pass the World Health Organisation suspensibility test after storing forLZA hours at 55 C. under pressure as specified by the World Health Organisation giving suspensibi-lities of 60% (3:1) and 54% (2:1) respectively, the test limit being 50%. This suspensibility test is carried out as follows: Suflicient powder to give 250 ml. of a suspension containing 0.5% gamma BHC is weighed accurately. It is pasted with 30 ml. hard water and allowed to stand at 30 .C. for liminutes. The slurry isrinsed into a 250 m1. measuring cylinder with water at 30 and the cylinder is filled to the 250 ml. mark. After being inverted through thirty complete cycles the'suspensionis allowed to stand for exactly half an hour when the top ninetenths of the suspension is sucked ofi. The BHC remaining in the 25 ml. residue is determined by any convenient method. The suspensibility is given by the following equation.

(b-a) X 100 Percent suspensibility: V bxg where a=weight of gamma BHC found in the'remaining onetenth of thesuspension. b=weight of gamma BI-IC in the sample used for the test.

Tables 1 and 2 are a'record of the vapour pressure resuitsv at C. which are obtained for gammav benzene hexachloride and gamma benzene hexachloride/resin mixtures after stated percentage evaporations in an ef- From a comparison. of data in Tables 1 and 2 it is seen that for a 3:1 gamma benzene hexachloride/resin mixture the gamma. benzene hexachloride/Cereclor 70 composition gives the best results and from a study of tion required for extreme persistence of deposits of gamma benzene hexachloride.

Also from pesticidal persistence tests carried out on surfaces of glass, filter paper and plaster of Paris with gamma benzenehexachloride and various resins and with diiferent ratios of gamma benzene hexachloride to the various resins it has been deduced that the most satisfactory dispersible pesticidal pulverulent compositions for filter paper and plaster of Paris surfaces are those containing gamma benzene hexachloride and a solid chlorinated parafiin wax, particularly Cereclor 70 and wherein the ratio of gamma benzene hexachloride to Cereclor 70 is not greater than 3:1.

Again from cooling curve tests of melts of gamma benzene hexachloride and Cereclor 70 mixtures it has been ascertained that whereas for 2:1 and 3:1 ratios of gamma benzene hexachloride to Cereclor 70 mixtures there are, well defined regions Where the gamma benzene hexachloride crystallises out there is no such well defined region for mixtures up to a 1:1 ratio of gamma benzene hexachloride to Cereclor 70.

A determination of the persistence of dispersible powder gamma benzene hexachloride formulations were carried out as follows.

fusion apparatus which is essentially similar to that described by Small; Small and Cowley (Trans. Faraday Soc, 1948; 44, 810) and in whichthe diameter of the bulb. is about 10 mm. and that of the hole in the bulb is 2.4 mm. Table 1 shows the efiectof difierent amounts amounts of fCereclor 70 to gammabenzene hexachlon'deon the vapour pressure of gamma benzene hexachloride and Table-2 shows the eifect of various resins in a 3:1 ratio of gamma benzene hexachloride to resin.

Solid solutions were made by fusing gamma benzene hexachloride with beta-naphthyl glycide ether, Aroclor 5 460 and Cereclor 70. The resultant solids were ground and formulated by milling with china clay as diluent, sodium naphthalene formaldehyde sulphonate and a sodium alkyl naphthalene sulphonate to give water disper'sible powders containing 50% organic component. Powders containing gamma benzene hexachloride and beta-naphthyl glycide ether in 2:1 and 1:1 ratios gave no increase in persistence on plaster of Paris surfaces after gamma benzene hexachloride dosages of lO'or 20 rug/sq; ft. Powders containing Aroclor 5460 or Cerecl-or 70 with gamma benzene hexachloride gave striking increases in persistence when tested on filter paper, and the -Cereclor 7O formulations also had high persistence on plaster of Paris, a relatively non-sorpti've surface.

Table 3 is a record 'of the time of exposure in minutes required to give a 50% knock-down of M. domestica as estimated from each graph which is obtained by plotting probit of percent knockdown against contact period in minutes for airing periods respectively of 1, 32, 60, and days with plaster of Paris test pieces treated with the dispersible powders gamma benzene hexachloride,

*fused gamma benzene hexachloride/Cereclor 70 (1: 1),

fused gamma benzene hexachloride/Cereclor 70 (2:1), fused gamma benzene hexachloride/Aroclor 5460 (2: 1)

and fused gamma benzene hexachloride/Aroclor 5460 (3:1) at 10.2 mg. gamma benzene hexachloride/ft Table 3 Exposure (min) required to give 50% knock-down of 1V1. domestz'ca Powder Surface after days airing gamma benzene hex- Plaster of 44 170 91 2, 692 1, 660

c r e Paris gamma benzene hexdo 118 50 31 72 398 achlorideI Cereclor 70 (1:1). gamma benzene hex- .do 55 50 32 102 295 achloridel Cereclor 70 (2:1). gamma benzene hexdo 44 178 85 2,951 1, 778

aclilorrde. gamma benzene hexdo 32 126 209 251 1, 514

achloridel Aroclor 5460 (2:1). gamma benzene hexdo 39 224 339 550 794 aohl0ride/ Aroclor 5460 (3:1).

mosquito Anopheles gambiae Giles was determined as follows. Sorptive mud blocks made from red lateritic soil from Babati and Tanganyika, 3 inches in diameter, were treated by pipette with aqueous suspensions of insecticide and the mosquitos exposed in Pespex chambers to the residues. Anopheles gambiae Giles is a resistant strain of mosquito and was chosen for these experiments in order to accelerate the test.

Groups of approximately 20 mosquitoes, of mixed sex, 1-2 days old, were used for each test, the exposure period (2-8 hours) being determined by the age of the residue.

All tests were carried out under constant temperature and humidity conditions (25 C. and 70% relative humidity). The blocks were stored under these conditions, the same blocks being used in successive tests.

Table 4 shows a comparison of the persistence of gamma benzene hexachloride with and without Cereclor 70 (1:1) at 50 ing/square foot on sorptive mud against Anopheles gambiae Giles (expressed in terms of percentage mortality).

What we claim is:

1. A water dispersible pesticidal pulverulent composition comprising a solid solution of gamma benzene hexachloride dissolved in solid chlorinated paraflin having an average chlorine content of about 70%, a freezing point between about 70 and 80 C. and a specific gravity of about 1.63 and in intimate association therewith characterized in that the pulverulent composition is water dispersible and in that the ratio of gamma benzene hexachloride to chlorinated paraffin in the admixture is such that for vapor pressures measured by elfusion at 50 C. the vapor pressure of the gamma benzene hexachloride is less than 75% of the vapor pressure of free gamma benzene hexachloride and after 25% has evaporated at 50 C. the vapor pressure is less than 25% of the vapor pressure of free gamma benzene hexachloride.

2. A water dispersible pesticidal pulverulent composition as claimed in claim 1 wherein in said admixture the ratio of gamma benzene hexachloride to chlorinated paraifin is such that the vapour pressure measured as aforementioned of the gamma benzene hexachloride is less than 20% of the vapour pressure of free gamma benzene hexachloride and after 6% has evaporated at 50 C. the vapour pressure is less than 8% of the vapour pressure of free gamma benzene hexachlot'ide.

3. A water dispersible pesticidal pulverulent composition as claimed in claim 1 wherein in said admixture the gamma benzene hexachloride and chlorinated parafiin in intimate association and in the aforesaid ratio are in the form of a powdered solidified melt of an admixture thereof.

4. A water dispersible pesticidal pulverulent composition as claimed in 1 wherein the gamma benzene hexachloride does not exceed 75% by weight on the combined weight of the gamma benzene hexachloride and the solid chlorinated paraffin.

5. A water dispersible pesticidal pulverulent composition as claimed in claim 4 wherein the gamma benzene hexachloride does not exceed 55% by weight on the combined weight of the gamma benzene hexachloride and the solid chlorinated paraflin.

6. A water dispersible pesticidal pulverulent composition as set forth in claim 1 in which the benzene hexachloride is present in the amount not greater than about 3 times the amount of said chlorinated parafiin.

7. The method of treating a sorptive surface with a pesticidal pulverulent composition which comprises applying to the sorptive surface a water dispersion of a composition comprising a solid solution containing gamma benzene hexachloride dissolved in solid chlorinated paraffin having an average chlorine content of about 70%, a freezing point between about 70 and C. and a specific gravity of about 1.63 and in intimate association therewith characterized in that the pulverulent composition is water dispersible and in that the ratio of gamma benzene hexachloride to chlorinated paratiin in the admixture is such that for vapor pressures measured by effusion at 5 0 C. the vapor pressure of the gamma benzene hexachloride is less than 75% of the vapor pressure of free gamma benzene hexachloride and after 25% has evaporated at 50 C. the vapor pressure is less than 25 of the vapor pressure of free gamma benzene hexachloride.

8. A Water dispersib'le pesticidal pulverulent composition comprising a solid solution of gamma benzene hexachloride dissolved in solid chlorinated paraflin having an average chlorine content of about 65-75%, a freezing point between about 70 and 80 C. and a specific gravity of about 1.63 and in intimate association therewith characterized in that the pulverulent composition is water dispersible and in that the ratio of gamma benzene hexachloride to chlorinated paraffin in the admixture is such that for vapor pressures measured by effusion at 50 C. the vapor pressure of the gamma benzene hexachloride is less than 75 of the vapor pressure of free gamma benzene hexachloride and after 25 has evaporated at 50 C. the vapor pressure is less than 25 of the vapor pressure of free gamma benzene hexachloride.

9. The method of treating a sorptive surface with a pesticidal pulverulent composition which comprises applying to the sorptive surface a water dispersion of a composition comprising a solid solution containing gamma benzene hexachloride dissolved in solid chlorinated paraffin having an average chlorine content of about 65-75%, a freezing point between about 70 and 80 C. and a specific gravity of about 1.63 and in intimate association therewith characterized in that the pulverulent composition is water dispersible and in that the ratio of gamma benzene hexachloride to chlorinated parafiinin the admixture is such that for vapor pressures measured by eifusion at 50 C. the vapor pressure of the gamma benzene hexachloride is less than 75% of the vapor pressure of free gamma benzene hexachloride and after 25% 'Burrage Sept. 26, 1950 Epstein Aug. 21, 1956 Galloway Aug. 15, 1961 FOREIGN PATENTS V Great'Brit-ain Sept. 25, 1947 'Great Britain Dec. 4, 1952 OTHER REFERENCES Hbmstei n et aL: I: of Economical Entomology, vol. 46, pages 937-940, 1953.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent. No. 3,035,970 May 22, 1962 Hyett. Henry Spendlove Bovingdon et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 1 and 2, for "Hyett Henry Spendlove, of Bovingdon, Maidenhead," read Hyett Henry Spendlove Bovingdon, of Maidenhead, in the heading to the printed specification, line 5, for "Hyett Henry spendl ove, Bovingdon, Maidenhead," read Hyett Henry Spendlove Bovingdon,

Maidenhead,

Signed and sealed this 18th day of September 1962.

(SEAL) Attest:

DAVID L. LADD ERNEST W. SWIDER Commissioner of Patents Attesting Officer 

1. A WATER DISPERSIBLE PESTICIDAL PULVERULENT COMPOSITION COMPRISING A SOLID SOLUTION OF GAMMA BENZENE HEXACHLORIDE DISSOLVED IN SOLID CHLORINATED PARAFFIN HAVING AN AVERAGE CHLORINE CONTENT OF ABOUT 70%, A FREEZING POINT BETWEEN ABOUT 70 AND 80*C, AND A SPECIFIC GRAVITY OF ABOUT 1.63 AND IN INTIMATE ASSOCIATION THEREWITH CHARACTERIZED IN THAT THE PULVERULENT COMPOSITION IS WATER DISPERSIBLE AND IN THAT THE RATIO OF GAMMA BENZENE HEXACHLORIDE TO CHLORINATED PARAFFIN IN THE ADMIXTURE IS SUCH THAT FOR VAPOR PRESSURE MEASURED BY EFFUSION AT 50*C, THE VAPOR PRESSURE OF THE GAMMA BENZENE HEXACHLORIDE IS LESS THAN 75% OF THE VAPOR PRESSURE OF FREE GAMMA BENZENE HEXACHLORIDE AND AFTER 25% HAS EVAPORATED AT 50*C, THE VAPOR PRESSURE IS LESS THAN 25% OF THE VAPOR PRESSURE OF FREE GAMMA BENZENE HEXACHLORIDE. 